Okay everyone, I've been havin problems with my HVAC system.
Yesterday I was drivin down the highway and felt a little hot air comin out of the vents (barely any although the selector was on high), so I switched the temp selector to cold just to see and sure enough it cooled down. Then I changed the vent selector to heater and the air came out of the heater vents instead, so I know it's not the vacuum leak I thought was the problem before.

I've been told to check the brown wire that supplies the 12V and it appears to not have been burnt at the connector, I'm gonna test it again just to make sure, but I want to check to see if something else could be wrong too. I'm thinking the only other options would be a loss of power to the switch or to the blower motor itself, or a bad blower motor.

In either of the 3 cases, how should I go about finding out which one is the culprit.

if it is the blower motor, where can I get one, how hard is it to replace by yourself and do you need anything other than basic sockets and drivers to do it?

Thanks in advance.
--Richie

 

well, its a small world because im having almost the exact same issue....but after 4 hours of troubleshooting today i think i can explain the system pretty good....

in a nutshell, 12vdc comes into ac control switch (elec switch that is operated when you select off/max/norm/etc)...when switch is off there is no voltage sent to blower motor....when you select any position besides OFF then 12vdc is sent through the brown wire into the blower switch (fan speed switch)......from here 12vdc is sent to blower motor via blower resistor ckt and/or high speed fan relay....this is determined by speed selected....low/2/3 speeds are all ran through blower resistors which are located to the right of blower motor in engine compartment.....high speed bypasses blower resistors and goes through the high speed fan relay which allows full speed of blower motor......

so which part failed.....heres easy way to figure it out....

on the blower motor itself there will be a 2wire plug....black wire is gnd and purple wire is 12vdc....just hookup 12vdc and ground directly to blower motor.....if it spins.....its good.....if it dont spin....its bad....

now assuming motor worked, does blower motor work on high speed......if so, i would look at blower resistors......if it works on low/2/3 speeds but not high then i would look at high speed relay.....

in my case, i had no blower motor at all but motor tested fine when i hooked it up hot.....so i backtracked problem to a toasted ac control switch.....which makes perfect since because it supplies 12vdc to blower fan switch and ultimately to blower fan......

id look there first, because ive got a 1991 formula and now a 1991 camaro b4c and both were the same part....$12 @ GM brand new!

hope this helps!
john

 

sounds about right to me. I checked it out today, had power all the way up to the blower motor, but no spin, so it must be the motor. Hopefully that's all, if not I think(hope) I can find it